Activation energy depends on

Minimum energy required for the reactant 'A' to convert to product 'B' is called thresold energy.Reactant 'A' has to gain an energy called activation enrgy, Ea to attain threshold energy.Thus lesser the activation energy greater will be the rate of chemical reaction.Activation energy of the reaction,is less because it involves lesser bond rearrangements.Activation energy of the reaction, is high because it involves more bond rearrangements.▬▬▬▬ (thick line) ...... Energy profile of uncatalysed reaction - - - - -  (dotted line) ..... energy profile of catalysed reaction.thus reaction proceeds faster in presence of catalyst.A catalyst lowers the activation energy of the reaction.Δ H (enthalpy of reaction) is unaffected by catalyst. Activation energy depends only on nature of reactants and catalyst.